When changing front and rear differential oils.

[Twodose]

1999 GMC Sierra 1500 4wd 5.3L.

 

The Haynes manual call for synthetic in the rear diff, the tag says 15-40mm  (0.6 in to 1.6 in)  below the hole for synthetic, how do you tell when it is at that level?

 

Is this also true for the front diff when using synthetic oil it it? < Haynes manual says bottom of the fill hole, but I’m assuming this is for regular oil since the manual does not call for synthetic in the front.

 

Also in the manual there are no capacities listed for front and rear diff, only the transfer case.

 

 

 

 

[txab]

Put synthetic in both. Same viscosity in both also. To follow the fill guidelines you reference, you can use an appropriate size allen wrench using the 90 degree bent portion. Just measure till you find one that is in the range or mark one. Also can use an arts and crafts pipe cleaner since it can be bent.

 

I think you'll end up needing 5 qts between both, iirc.

 

Amsoil.com has a good reference page for your truck capacities

[Twodose]

So you are saying on the front fill to the bottom of the fill hole?

Also I have a 10 bolt rear with 3.73 gears rpo code gt4, how do you tell if it is 8.50 or 8.62 or what size it is.

thank you for your reply, it was very helpful.